Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2002 Oct;120(4):497–508. doi: 10.1085/jgp.20028573

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

Copyright © 2002, The Rockefeller University Press

This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).

PMC Copyright notice

Figure 8. — Reaction scheme for extracellular cations binding to the Na pump. The scheme depicted describes the enzyme conformation that has just translocated and released Na to the extracellular space. We have purposefully omitted references to E1 and E2 as they are sometimes used to describe different pump conformations. Also, this model assumes that rubidium and sodium are mutually exclusive. Rubidium binds much better to the protonated pump than the unprotonated pump, 13-fold better in rat (a) and 34-fold better in human (b). In contrast, sodium binds only 1.34-fold better to the protonated pump than the unprotonated pump in human. In rat, the effect of protons is in the opposite direction, making sodium bind sevenfold less well. In both species, the addition of protons greatly increases the selectivity of the pump for rubidium over sodium. Stated another way, the pK changes substantially in both species when rubidium binds instead of sodium. The reaction scheme shows the K _d values for proton binding to the different cation loaded, outward facing, conformations and also the pK values. Values obtained from Figs. 2, 4, 5, and 6, using the equations in materials and methods as described in the text.

Figure 8. — Reaction scheme for extracellular cations binding to the Na pump. The scheme depicted describes the enzyme conformation that has just translocated and released Na to the extracellular space. We have purposefully omitted references to E1 and E2 as they are sometimes used to describe different pump conformations. Also, this model assumes that rubidium and sodium are mutually exclusive. Rubidium binds much better to the protonated pump than the unprotonated pump, 13-fold better in rat (a) and 34-fold better in human (b). In contrast, sodium binds only 1.34-fold better to the protonated pump than the unprotonated pump in human. In rat, the effect of protons is in the opposite direction, making sodium bind sevenfold less well. In both species, the addition of protons greatly increases the selectivity of the pump for rubidium over sodium. Stated another way, the pK changes substantially in both species when rubidium binds instead of sodium. The reaction scheme shows the K _d values for proton binding to the different cation loaded, outward facing, conformations and also the pK values. Values obtained from Figs. 2, 4, 5, and 6, using the equations in materials and methods as described in the text.